As is known, virtually all residential homes utilize electrical power received from a utility company. Typically, utility companies have an excellent record of providing uninterrupted or infrequently interrupted power to their customers at proper voltage levels and line frequency. However, due to the increasing demand for power, power outages have become more frequent. While power outages usually last only for a short duration, an extended power outage may cause more than simple aggravation for customers of the utility. A power outage may render a homeowner's appliances, such as the sump pump, refrigerator, freezer, or air conditioner inoperable.
In order to combat these occasional disruptions in service, many residential customers of the utility companies have equipped their homes with standby electric generator systems. These standby electric generator systems include internal combustion engines that drive electric generators. If the commercial power from the utility company fails, the internal combustion engine of the standby electric generator system is automatically started causing the electric generator to generate electrical power. When the electrical power generated by the electric generator reaches the proper voltage and frequency desired by the customer, a transfer mechanism transfers the load imposed by the homeowner from the commercial power lines to the electric generator.
Typically, the transfer mechanism incorporates switches that isolate the electrical power supplied by the utility company from the generator. In a residential application, the switches are flipped either manually or automatically between the utility source and the generator in order to provide power to the electrical system of the home. These prior art transfer mechanisms transfer the entire electrical system of the home onto the generator. Recent changes to the National Electric Code have mandated that newly installed standby electric generators must be sized to carry the entire load to which the generator may be connected. It can be appreciated that the demands of the entire electrical system of a home can be quite significant. As a result, the generator must be of sufficient size to power the entire electrical system of the home. This, in turn, increases the overall cost of the standby electric generator system for the homeowner.
This can be particularly problematic for homes that have two or more central air conditioners to supply conditioned air to multiple zones within a home. The standby electric generator system must be capable of handling the current demands of both air conditioners if the air conditioners are to be powered in the event utility power has been interrupted. As known in the art, an air conditioner, when actively providing conditioned air, has a relatively large current draw. For those homes having two air conditioner units, the demands on the standby electric generator when both units are operating can be particularly large and, in some cases, may overload the generator. As a result, larger standby electric generators are required for dwellings having multiple air conditioning units.